Protective laminates

ABSTRACT

Protective laminates are provided that include (a) a layer that is breathable, free-standing, and highly impermeable to chemicals to a degree that is subject to reduction upon flexing of the highly impermeable layer alone; and (b) a non-textile layer attached to the highly impermeable layer, the non-textile layer tending to mitigate the reduction in the impermeability of the highly impermeable layer if the laminate is flexed. The laminates may, for example, be attached to textiles and used in protective fabrics.

TECHNICAL FIELD

This invention relates to protective laminates.

BACKGROUND

Protective garments, e.g., garments used by emergency workers, are generally made of fabrics that protect the wearer from the conditions the wearer expects to encounter, e.g., heat and flame in the case of firefighting garments. The fabrics used in such garments are typically waterproof and allow water vapor to pass from inside to outside the garment to provide comfort to the wearer during periods of exertion. An example of a waterproof breathable laminate produced from an expanded polytetrafluoroethylene (“ePTFE”) membrane is disclosed in U.S. Pat. No. 4,194,041. In this structure, the pores of the ePTFE are protected by a hydrophilic polyurethane layer, to prevent the pores of the ePTFE from becoming contaminated by lower surface energy liquids. Lower surface energy liquids tend to wet out untreated microporous structures, thereby reducing the hydrostatic resistance of the membrane and corresponding laminate structure.

Fabrics for protective garments may include a textile layer and a layer of a protective film that provides waterproofing. The protective film may be, for example, a treated micro-porous film, e.g., a film that has pores sized to permit vapor molecules to pass, while blocking water molecules, but has its surface energy modified to reduce its ability to wet out. Alternatively, the protective film could be a monolithic layer produced from a hydrophilic material such as polyurethane, nylon, or PEBAX polymer.

In many applications, it is necessary that the fabric be highly chemically resistant. For example, the Standard on Protective Ensemble for Structural Fire Fighting published by the National Fire Protection Agency (NFPA 1971, 2000 Edition) require the moisture barrier layer of fire fighting garments to resist penetration by a list of chemicals in accordance with ASTM F903 (Standard Test Method for Resistance of Protective Clothing Materials to Penetration by Liquids). Other applications, such as military applications and hazardous waste clean-up, also require high chemical resistance, but may not allow for effective transport of moisture, leading to heat stress.

It is important that fabrics used in protective garments be capable of withstanding laundering without loss of chemical resistance or de-lamination of the protective film from the textile.

SUMMARY

The inventors have found that certain chemically resistant breathable films are relatively brittle and may fracture easily when flexed under certain conditions. This brittleness may render fabrics including such films subject to a decrease in chemical impermeability after laundering, due to the impact of the wet environment of laundering on the physical properties of the film. Some chemically resistant breathable films are also subject to a decrease in their impermeability as a result of flexing under dry conditions. The inventors have addressed this problem by providing protective laminates including a highly impermeable layer and a non-textile layer that tends to mitigate the reduction in the impermeability of the highly impermeable layer if the laminate is flexed.

In one aspect, the invention features a protective laminate that includes (a) a layer that is breathable, free-standing, and highly impermeable to one or more chemicals to a degree that is subject to reduction as a result of flexing of the highly impermeable layer alone; and (b) a non-textile layer attached to the highly impermeable layer, the non-textile layer tending to mitigate the reduction in the impermeability of the highly impermeable layer that is a result of flexing of the laminate.

The term “breathable,” as used herein, refers to the moisture vapor transmission rate (MVTR) of a material. A breathable film preferably has a MVTR of at least 200 g/m²/day, measured by ASTM E96B.

The term “free-standing,” as used herein, refers to a film that has sufficient structural integrity to be separated and tested, independently of external support, for its resistance to flex fatigue and its chemical penetration resistance. The film would also be capable of being attached to another film, for example using a lamination process such as joining the two films using an adhesive.

The phrase “highly impermeable to one or more chemicals,” as used herein, means that the layer would significantly inhibit the flow of harmful chemicals from one side of the layer to the other. Preferably, impermeability is sufficient to comply with the liquid penetration resistance requirement associated with NFPA 1971, 2000 edition. Some highly impermeable layers may also comply with the chemical penetration resistance test required by NFPA 1994, as tested according to ASTM F739.

The phrase “subject to reduction upon flexing of the highly impermeable layer alone,” means that if the highly impermeable layer is not attached to the support layer, the chemical resistance of the highly impermeable layer will be deleteriously affected by flexing the highly impermeable layer. In some cases, the reduction in chemical resistance may occur after only a single flexing.

The term “non-textile” refers to a sheet material that is not fibrous, and excludes, for example, woven and non-woven fibrous sheet materials The phrase “mitigate the reduction in the impermeability” means that the reduction in impermeability that would occur upon flexing of the highly impermeable layer alone is reduced to a measurable extent when the protective laminate is tested, before and after repeated flexing, under the same conditions using the same test procedure. Testing may be performed, for example, using a Newark Flexing Machine according to the test procedures specified in ASTM D2097, under the environmental conditions specified in ASTM D1610.

The term “layer” refers to a discrete region of material, which, unless otherwise noted (e.g., by specifying that the layer is free-standing), may be in the form of a film, coating, deposit, or any other desired form.

Some implementations include one or more of the following features. The laminate may further include a second non-textile layer, and the highly impermeable layer may be interposed between the non-textile layers. Alternatively, the laminate may further include a second highly impermeable layer, and the non-textile layer may be interposed between the highly impermeable layers. The laminate may further include a textile layer attached to the highly impermeable layer or the non-textile layer, e.g., to form a protective fabric. The protective laminate may have a MVT of at least 200, preferably at least 2000. The layers may each individually have a MVT of at least 200. The layers may each be microporous or monolithic. The highly impermeable layer may have a thickness of about 0.005 to about 0.050 mm. The non-textile layer may have a thickness of about 0.005 to about 0.050 mm. The laminate may further include an adhesive layer attaching the non-textile layer to the highly impermeable layer. The adhesive layer may be discontinuous. Alternatively, the non-textile layer may be bonded directly to the highly impermeable layer, without intervening adhesive. The non-textile layer may comprise a free-standing film, for example a film selected from the group consisting of polyurethane films, expanded PTFE films, polyester films, nylon films, polyether block amide films, and polyethylene films. The non-textile layer may be hydrophilic.

In another aspect, the invention features a method including bonding a layer that is breathable, free-standing, and highly impermeable to chemicals to a degree that is subject to reduction upon flexing of the highly impermeable layer, to a non-textile layer, the non-textile layer tending to mitigate the reduction in the impermeability of the highly impermeable layer if the laminate is flexed.

Some implementations may include one or more of the following features. The bonding step may include applying an adhesive to one or both layers. The adhesive may be applied in a discontinuous pattern. The adhesive may be applied in a continuous pattern using a hydrophilic polymer. The adhesive may be applied by gravure printing. The bonding step may include thermally bonding the non-textile layer directly to the highly impermeable layer.

In a further aspect, the invention features articles made with the protective laminates. For example, the invention features an article including: (a) a protective laminate that includes (i) a layer that is breathable, free-standing, and highly impermeable to chemicals to a degree that is subject to reduction upon flexing of the highly impermeable layer alone; and (ii) a non-textile support layer attached to the highly impermeable layer, the non-textile layer tending to mitigate the reduction in the impermeability of the highly impermeable layer if the laminate is flexed; and (b) a textile layer, attached to the protective laminate to form a chemically resistant fabric, the chemically resistant fabric being configured to define the article.

The article may be, for example, a protective structure such as a tent, a garment such as a jacket, pair of pants or glove, or an insert for footwear.

Among the advantages of the invention may be one or more of the following.

In some implementations, the protective laminates are selectively permeable, i.e., they exhibit high moisture vapor transmission rates, while also being able to restrict the passage of harmful chemicals, even under conditions where a pressure differential exists. The laminates may be attached to a textile layer for use in articles such as protective garments, tents and accessories that may be subjected to adverse conditions. Some laminates, when attached to a textile layer, provide excellent chemical resistance even after repeated launderings and/or other flexing such as may occur during use of a garment. In some implementations, fabrics including the protective laminate meet NFPA standards for flame-retardancy and chemical resistance. The laminates are waterproof and breathable. In some cases, the laminates may meet the requirements of the chemical penetration resistance test required by NFPA 1994, as tested according to ASTM F739. The laminates can be produced repeatably and predictably. The laminates are easily stored, shipped, and manipulated during lamination to a textile layer. The barrier properties of the laminate are maintained prior to lamination to a textile layer. In certain applications, such as semi-durable and durable garments, it is useful to achieve resistance to water penetration and provide chemical resistance after multiple launderings. In military applications, a minimum of 6 wash/dry cycles is typically requested, whereas in the Fire Service the chemical penetration testing is done after 5 wash/dry cycles complying with a procedure specified in AATCC 135. Fabrics produced with some protective laminates may protect the wearer of a garment or contents of a protective structure from noxious gases, such as Sarin, Mustard, and VX nerve agents and other noxious chemical agents. Fabrics produced with some protective laminates may show no evidence of penetration of a solution consisting of 75% diethyltoluamide (DEET) and 25% ethanol before and after laundering when tested according to paragraphs 4.4.2.6 and 4.4.14 of MIL-DTL-31011A.

The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features and advantages of the invention will be apparent from the description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a diagrammatic, highly enlarged exploded side view of a protective fabric including a protective laminate.

DETAILED DESCRIPTION

A fabric 10, for use, e.g., in a protective garment, is shown diagrammatically in FIG. 1. Fabric 10 includes a protective laminate 12 and a textile layer 14. In this embodiment, protective laminate 12 includes a barrier layer 16 interposed between two support layers 18 and 20. While the layers of fabric 10 are exploded in FIG. 1, for clarity, in the finished fabric all of the layers would be attached to each other, e.g., by adhesive or lamination as will be discussed below. Typically, one of the layers of the protective laminate is attached to a textile, forming a preliminary laminate, and then the other layers are applied to this preliminary laminate. However, if desired all of the layers can be laminated together in a single processing step or in a different order of steps.

Barrier layer 16 is a free-standing film prior to being attached to the support layers. Suitable barrier layers are highly impermeable to chemicals. It is generally preferred that the barrier layer comply with the liquid penetration resistance requirement associated with NFPA 1971, 2000 edition.

Suitable barrier layers may be relatively brittle, and thus tend to exhibit a reduction in chemical impermeability when flexed, as discussed above. For example, the barrier layer, when tested alone, may exhibit visually observable cracking after 50 to 500 cycles using a Newark Flex Tester according to the test procedure specified in ASTM D2097, under the environmental conditions specified in ASTM D1610. The barrier layer typically has a thickness of less than about 0.05 mm, e.g., from about 0.005 to 0.050 mm.

Suitable barrier films are breathable, i.e., they have an MVTR of at least 200 g/m²/day, measured by ASTM E96B. In some implementations, the barrier layer has an MVTR of from about 200 to 5000. The barrier layer may be monolithic or microporous.

One suitable barrier layer is a polyether sulfone (PES) film that is treated with a fluoropolymer to modify its surface energy, commercially available from Pall Corp. under the tradename SUPOR. Another suitable barrier layer is commercially available from DuPont under the tradename NAFION. This barrier layer is a perfluorosulfonic acid film (tetrafluoroethylene/perfluoro (4-methyl-3,6-dioxa-7-octene-1-sulfonic acid) copolymer), CAS Number 31175-20-9. The NAFION films have a tensile modulus (ASTM D 882) at 23° C. and 50% RH of about 249 MPa, a tensile modulus at 23° C. when water soaked of about 114 MPa, and a tensile modulus at 100° C. when water soaked of about 64 MPa. The elongation at break (ASTM D 882) shows a similar decrease when the films are water soaked. The NAFION films exhibit an elongation at break at 23° C. and 50% RH of about 225% in the machine direction and 310% in the transverse (cross-machine) direction, an elongation at break at 23° C. when water soaked of about 200% in the machine direction and 275% in the transverse direction, and an elongation at break at 100° C. when water soaked of about 180% in the machine direction and 240% in the transverse direction. Other properties of the NAFION films include an MVTR of about 4000 g/m²/day, a basis weight of about 100 to 500 g/m², and a thickness of about 50 to 250 microns.

The support layers 18 and 20 may be the same or different. One or the other of the support layers may be omitted. Thus, the protective laminate may include only inner support layer 18, leaving barrier layer 16 exposed (i.e., the fabric 10 includes an inner support layer 18 interposed between a barrier layer 16 and a textile layer 14), or the protective laminate may include only outer support layer 20, so that the barrier layer 16 is in direct contact with the textile layer 14 in the finished fabric (i.e., the fabric 10 includes a barrier layer 16 interposed between an outer support layer 20 and a textile layer 14). Other configurations may also be possible.

Suitable materials for use in the support layer(s) include films and other materials that will mitigate the reduction in chemical impermeability of the barrier layer when the protective laminate is flexed. Preferred support layer materials will substantially eliminate the reduction in impermeability over a large number of flex cycles, i.e., will mitigate the reduction in impermeabilty sufficiently so that the protective laminate will still pass the liquid penetration resistance requirement associated with NFPA 1971, 2000 edition even after repeated flexing. In some implementations, the support layer may increase the number of flex cycles prior to visually observable cracking by over 100%. The use of support layers on both sides of the barrier layer may increase the number of flex cycles by over 500%, in some cases by over 1000%.

The support layer typically has a thickness of less than about 0.07 mm, e.g., from about 0.005 to 0.050 mm.

Suitable materials for use as support layers are breathable, i.e., have an MVTR of at least 200 g/m²/day, measured by ASTM E96B. It is generally preferred that the breathability of the support layer be similar to or greater than that of the barrier layer. Thus, the breathability of the support layer is generally in the range of about 200 to 5000. If desired, the layers of the laminate may have different levels of breathability, provided the overall breathability of the laminate is adequate for its intended use. The support layer may be monolithic or microporous, and may be a film or other continuous or discontinuous sheet material. When the protective laminate includes two support layers, as shown in FIG. 1, one can be monolithic and the other can be microporous, or both can be monolithic or microporous.

An example of a suitable film is TX1540 film, commercially available from Omniflex under the tradename TRANSPORT. This film is a hydrophilic polyurethane, having a 100% modulus of about 550-650 psi and a thickness of about 0.0005-0.025 mm.

Other suitable films for use as support layers include other hydrophilic polyurethane films, e.g., TX1530 film, commercially available from Omniflex; microporous polyurethane, e.g., P3 series films commercially available from Porvair; expanded polytetrafluoroethylene (ePTFE), e.g., ePTFE films commercially available from W. L. Gore, Tetratec and BHA; hydrophilic co-polyester films, e.g., SYMPATEX films from Sympatex Technologies and HYTREL films from DuPont; nylon films, e.g., TX3050 films commercially available from Omniflex; polyether block amide films, e.g., TX4100 films commercially available from Omniflex and films formed from PEBAX resins (Atofina); and microporous polyethylene films. Other suitable hydrophilic polyurethane films include films formed from 58245 resin, commercially available from Noveon.

In most cases, the support layer will have a lesser degree of chemical impermeability to certain chemicals than the barrier layer. In such cases, the support layer may not, by itself, have adequate chemical impermeability for use in the application for which the protective laminate is intended.

The textile layer may be any desired textile, including woven, knitted and nonwoven materials and composites of such materials. The textile may be selected based on the properties required for a given application, e.g., flame and/or heat resistance, thermal properties, comfort, weight, and moisture vapor transmissivity. Suitable textiles include 332N NOMEX fabric, available from Southern Mills, NYCO fabric, available in a camouflage print from Bradford Dye, and 70d taslanized nylon. Other suitable textiles include nonwovens such as VILENE nonwoven, commercially available from Freudenberg, and E89 nonwoven, commercially available from DuPont. The textile layer generally has a thickness of from about 0.1 to 1.0 mm. The textile layer generally does not contribute significantly to the mitigation of the loss of chemical impermeability of the barrier layer, but does frequently offer physical protection against abrasion tear and puncture.

The fabric 10 (textile layer and protective laminate) will typically have an MVTR of at least 200 g/m²/day as measured by ASTM E96B. In some implementations, the MVTR will be from about 200 to 5000 g/m²/day, e.g., from about 1000 to 3000 g/m²/day. The fabric 10 will generally comply with the liquid penetration resistance requirement associated with NFPA 1971, 2000 edition, and with other industry standards regarding impermeability, for example chemical penetration after laundering according to the laundering procedure specified in AATCC 135.

Various techniques may be used to join the layers of the protective laminate, and to join the protective laminate to the textile layer. For example, the support layer(s) may be bonded to the barrier layer using an adhesive, such as a solvent based crosslinking polyurethane adhesive, a reactive hot melt-polyurethane adhesive, or a thermoplastic adhesive, e.g., a thermoplastic polyester, polyurethane, nylon or olefinic adhesive supplied, for example, as a hot melt, film, or powder- or web-based system.

The adhesive may be applied as a discontinuous layer to one or both of the layers to be adhered, e.g., using direct gravure printing. The discontinuous adhesive may be applied in any desired pattern, e.g., lines, dots, polygons, or other shapes. Suitable methods for applying an adhesive in a discontinuous pattern are described, for example, in U.S. Pat. No. 5,874,140, the disclosure of which is incorporated by reference herein.

Alternatively, the layers may be thermally fused or pressure laminated, without any intervening adhesive. The process parameters for this operation will vary depending on the materials used for the support and barrier layers, and would be selected to provide good adhesion without significant damage or deterioration of any of the layers.

The following examples are intended to be illustrative and not limiting in effect.

EXAMPLE 1

A protective laminate was formed using a multi-pass process, as follows:

Pass 1: A barrier film (0.019 mm perfluorosulfonic acid, commercially available from Dupont under the tradename NAFION) was laminated to a woven textile layer known in the trade as NYCO and manufactured from a blend of cotton, nylon and a small percentage of carbon fiber. The film was printed with a solvent-based crosslinking polyurethane adhesive system having a viscosity of 15,000 to 25,000 cps on a gravure applicator with a discontinuous dot pattern. The film and textile layer were combined in a nip at a processing speed of 10 to 20 yards per minute. The adhesive was then allowed to cure for a few days.

Pass 2: The film side of the barrier/textile laminate created in Pass 1 was printed with adhesive as described above in Pass 1, and the barrier/textile laminate was combined with a support layer (a 0.005 mm hydrophilic polyurethane film having a Shore hardness of 80A and a 100% modulus of 550-650 psi, commercially available from Omniflex under the tradename Transport TX1540) at a processing speed of 10 to 20 yards per minute.

EXAMPLE 2

A laminate was made as discussed in Example 1 above, except that in Pass 1 the barrier film used was a polyether sulfone (PES) film that is treated with a fluoropolymer to modify its surface energy, commercially available from Pall Corp. under the tradename SUPOR.

EXAMPLE 3

To test the effect of providing a support layer on the flexural properties of barrier layers, the support layer described above in Example 1 was laminated to one side and to both sides of the barrier films described in Examples 1 and 2. The textile layer was omitted.

These laminates were flex tested through multiple flexing cycles using a Newark Flexing Machine according to the procedure specified in ASTM D2097, under the ambient conditions specified in ASTM D1610. As a control, the two barrier layers were individually subjected to the same testing. The samples were observed visually, and were deemed to have failed on the cycle at which the first visually observable cracking occurred.

The results of this testing were as follows: the NAFION barrier layer alone withstood 87 cycles, while the PES barrier layer alone withstood 394 cycles. Adding a single support layer increased the number of cycles before failure by 887% and 33%, respectively. Adding support layers on both sides of the barrier film increased the number of cycles before failure by 1817% and 599%, respectively.

A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention.

For example, while the support layer has been described above as a film, in some cases the support layer may be a coating. The coating may be formed by applying a liquid directly to the barrier layer, or by casting the liquid onto a release surface and then transferring the cast coating from the release surface to the barrier layer. The liquid may be a polymeric solution. For example, a polymer such as a thermoplastic polyurethane, e.g., polymers commercially available from Noveon under the designations 58245 or 58237, may be solvated and the solution may be cast and transferred as described above. Suitable coatings include, for example, hydrophilic polyurethane systems, such as the HYPOL series available from Dow Chemical or COMFORTEX 52158, available from Raffi & Swanson. The typical application weight is generally from about 0.2 oz/sq.yd. to 1.0 oz/sq.yd.

Moreover, in addition to the arrangements discussed above (support layers on one or both sides of a single barrier layer) other arrangements are possible. For example, a single support layer can be interposed between two barrier layers, e.g., if it is desirable to protect the support layer from exposure to chemicals. One or more additional support and/or barrier layers may be included in any of these arrangements. Also, while a single textile layer is shown in FIG. 1 and described above, the fabric may include multiple textile layers on a single side of the protective laminate, or the protective laminate may be interposed between multiple textile layers.

The resulting fabric can be used in any desired manner. For example, the fabric can be cut according to a pattern, and the patterned pieces can then be sewn to form a garment. The fabrics are suitable for use in protective garments. In some implementations, the fabrics are suitable for use in garments for applications such as firefighting, hazardous waste cleanup, and environmental remediation.

Accordingly, other embodiments are within the scope of the following claims. 

1. A protective laminate comprising a layer that is breathable, free-standing, and highly impermeable to chemicals to a degree that is subject to reduction upon flexing of the highly impermeable layer alone; and a non-textile layer attached to the highly impermeable layer, the non-textile layer tending to mitigate the reduction in the impermeability of the highly impermeable layer if the laminate is flexed.
 2. The protective laminate of claim 1 further comprising a second non-textile layer, wherein the highly impermeable layer is interposed between the non-textile layers.
 3. The protective laminate of claim 1 further comprising a second highly impermeable layer, wherein the non-textile layer is interposed between the highly impermeable layers.
 4. The protective laminate of claim 1 further comprising a textile layer attached to the highly impermeable layer.
 5. The protective laminate of claim 1 further comprising a textile layer attached to the non-textile layer. 